Leonardo da Vinci’s bat-winged flying-machine design was an ornithopter.
An ornithopter is an aircraft intended to fly by flapping wings, rather than by using fixed wings like an airplane or rotating blades like a helicopter. Leonardo studied birds and bats because he believed their wing movements could inspire human flight.
His notebooks contain several ornithopter concepts, including machines with large wings operated by a person’s arms and legs. These designs were never successfully built or flown, partly because human muscles cannot provide enough power for a practical flapping aircraft of that size.
Leonardo’s sketches are sometimes called inventions even when they were theoretical designs. The term “ornithopter” describes the type of machine, not a specific Leonardo model. Modern ornithopters have been built as experimental aircraft and small radio-controlled machines, but they do not prove that Leonardo’s original designs would have worked.